The present invention relates to an automatic patient control device that delivers a medium to a patient.
Gaymar Industries, Inc. (the assignee of the present invention) is the owner and manufacturer of the MEDI-THERM II(copyright) hypo/hyperthermia machine. This machine delivers water to a blanket (i.e., Gaymar""s Hypo/hyperthermia blanket, Gaymar""s THERMACARE(copyright) blanket or Gaymar""s MEDI-TEMP(copyright) blanket), a mattress pad (i.e., Gaymar""s Alternating Pressure Pad (model no. EFF302)), a chair pad, or a mattress unit (i.e., Gaymar""s CLINIDYNE(copyright) mattress) (collectively the blankets, pads, and mattresses and obvious variations thereof are hereinafter xe2x80x9cObjectsxe2x80x9d). In particular, the Objects surround a patient or applied to predetermined portions of the patient.
The object of the MEDI-THERM II(copyright) hypo/hyperthennia machine is to stabilize a patient who is experiencing hypothermia or hyperthermia or, in some instances, to actively cause hypothermia or hyperthermia as therapy. To understand the MEDI-THERM II(copyright) device, we will revert to FIG. 1 (prior art) which is a flow diagram of how the MEDI-THERM II(copyright) device distributes water to and from an Object. The liquid medium enters MEDI-THERM II(copyright) device through return inlet 52. From return inlet 52, the liquid medium traverses through a first conduit 30 to a first solenoid valve 32 for cold liquid medium or a second solenoid valve 34 for warm liquid medium.
From the first solenoid valve 32, the liquid medium goes through a second conduit 36 and a first cold inlet 37 to a cold reservoir 38. The cold reservoir 38 is a conventional cooling unit that cools the water, i.e., a refrigeration system""s or air conditioner""s evaporator. The evaporator in the reservoir maintains a large quality of water at a predetermined temperaturexe2x80x94normally 4xc2x0 C.xe2x80x94(hereinafter xe2x80x9cCold Waterxe2x80x9d). Water entering the reservoir is cooled by mixing with the Cold Water already in the reservoir (hereinafter xe2x80x9cReservoir Waterxe2x80x9d.) If the cold reservoir 38 overflows, the Cold Water escapes from the device 10 through an overflow outlet 40. The Cold Water then flows through a cold outlet 41 of the cold reservoir 38 and a third conduit 42 to a manifold 44.
Similarly from the second solenoid 34, the water goes to a hot reservoir 46 through a fourth conduit 48 and a hot inlet port 49. The hot reservoir 46 is a conventional heating apparatus that heats the liquid medium (hereinafter xe2x80x9cWarm Waterxe2x80x9d). The Warm Water flows through the warm outlet 56 to the manifold 44.
At the manifold 44 the Warm Water and the Cold Water converge. The selection of which return water path is active and its length of time active is controlled via solenoid valves 32 and 34 to attain a desired temperature (hereinafter xe2x80x9cMixed Waterxe2x80x9d). The Mixed Water is drawn through a sixth conduit 74 by a conventional pump 76, to supply outlet 14. A flow switch 78 on the sixth conduit 74 senses whether the Mixed Water reaches the supply outlet 14. Obviously, when the flow switch 78 is on, the Mixed Water reaches the supply outlet 14. And when the flow switch 78 is off, the Mixed Water fails to reach the supply outlet 14. A seventh conduit 80 connects with the first conduit 30 to provide quelling of temperature overshoot when no Object is connected.
When the Mixed Water reaches the supply outlet 14, the Mixed Water is released into the outlet conduit 18 into the Object 16. The Mixed Water traverses through the Object 16 to the return conduit 50 and into the return inlet 52.
The Mixed Water temperature is altered with the first solenoid valve 32 which controls the Warm Water and the second solenoid valve 34 which controls the Cold Water. The amount of water each valve 32, 34 allows into the manifold 44 depends on the temperature of the mammal 20 and the temperature of the Mixed Water in the Object.
The temperature of the mammal 20 is measured by a first conventional temperature sensing device (i.e. thermistors or thermocouples) 130 connected to a preselected portion of the mammal 20 and interconnected to a processing unit 90. The measurement from the first temperature sensing device 130 is transmitted to a processing unit 90.
The temperature of the Mixed Water in the Object is measured by a second conventional temperature measuring device 132 placed in the Object 16, in the supply conduit 18, the supply outlet 14, the sixth conduit 74, or manifold 44. The measurement from the second temperature measuring device 132 is transmitted to the processing unit 90.
The processing unit 90 compares the measurement from the first temperature sensing device 130 (hereinafter xe2x80x9cFirst Measurementxe2x80x9d) to the Set Point Body temperature of the mammal 20 (hereinafter xe2x80x9cSet Point Body Temperaturexe2x80x9d). The processing unit 90 determines whether First Measurement is above or below the Set Point Body Temperature.
Initially when the First Measurement is above the Set Point Body Temperature, the MEDI-THERM II(copyright) device, by design, applies the coldest water available (normally 4xc2x0 C.) to the Object 16. FIG. 2 (prior art) illustrates this design feature in section 200 wherein the temperature of the First Measurement is represented as line 201, the Set Point Body Temperature is represented as line 202, and the Mixed Water is represented as line 203. Once the First Measurement 201 falls below the Set Point Body Temperature 203, the processing unit uses the solenoid valves 32, 34 to alter the temperature of the Mixed Water, not at a predetermined differential from the First Measurement, to eventually stabilize the patient to the Set Point Body Temperature. See section 204 of FIG. 2.
Likewise, when the First Measurement is below the Set Point Body Temperature, the MEDI-THERM II(copyright) device, by design, applies the warmest water available (normally 42xc2x0 C.) to the Object 16. Once the First Measurement 201 falls above the Set Point Body Temperature 203, the processing unit uses the solenoid valves 32, 34 to alter the temperature of the Mixed Water, not at a predetermined differential from the First Measurement, to eventually stabilize the patient to the Set Point Body Temperature. See section 204 of FIG. 2.
The MEDI-THERM II(copyright) device, however, can sometimes cause discomfort to the patient. This discomfort can occur when the MEDI-THERM II(copyright) device applies the coldest water available (normally 4xc2x0 C.) or the warmest water available (normally 42xc2x0 C.) into the Object during the initial time frame, shown in section 200 of FIG. 2, or when the First Measurement and the Set Point Body Temperature difference is not-so-great but exists for a long time. When the patient is exposed to the coldest or warmest water available, the patient may experience some discomfort.
The present invention solves this problem.